"Light", as used herein, includes the visible, near infrared and near ultraviolet portions of the spectrum. The present invention relates to a light source device for use in any application where a higher intensity (i.e., brighter), non-laser light source than previously attainable would be a benefit. One such application is for use with endoscopes (of either the electronic endoscope, fiberscope or rigid endoscope variety). Another important application is as a light source for short range navigational aids, especially during periods of reduced visibility. In such a use, the invention could increase the minimum visibility required to land an aircraft safely, and reduce the risk of grounding or collision of ships entering harbors during periods of fog. Another important potential use of the invention is as a light source for high intensity spotlights in various commercial, law enforcement, and military applications.
In recent years, endoscopes for various types of medical diagnosis and/or treatment have been widely employed. They generally are inserted into a body cavity for observing vicera by the insertion of a long and narrow insertion component. Conventionally, light source devices for these types of endoscopes arrange reflectors that collect light emitted to the rearward direction of a lamp and reflect the light onto an end surface of a light guide. The light guide also receives part of the light emitted in the forward direction from the lamp.
However, only light within a maximum "acceptance cone" (specified by what is termed in the art as "numerical aperture") is transmitted by a light guide. Since the numerical aperture of a light guide is generally small, with this type of conventional light source, a portion of the light emitted in the forward direction from the lamp that is incident on the end of the light guide is not able to be transmitted by the light guide and is instead scattered. Thus, it is very difficult to effectively transfer the light emitted from a light source into a light guide. Therefore, various light source devices have been proposed in order to solve this problem. Of these, a few examples will be described herein.
FIG. 8 illustrates a light source device described by Japanese Utility Model Laid-Open Publication No. 62-106207. With such a light source device, in addition to a reflector 2 which is arranged in the rearward direction of the lamp 1, a reflector 3 is arranged in the forward direction of the lamp 1. Light emitted by the lamp 1 in the forward direction is reflected by the reflector 3, and is again reflected by the reflector 2 so as to be incident on an end surface of the optical fiber 4 within the maximum cone angle of acceptance, thereby raising the utilization efficiency of the light.
FIG. 9 illustrates a light source device disclosed by Japanese Patent Laid-Open Publication No. 5-40223. A lamp 1 is attached in the vicinity of a first focus position of ellipsoidal reflector 5, and a spherical, concave reflector 6 having an axial aperture 6a in the forward direction of the ellipsoidal reflector is arranged so that the center of curvature of the reflector 6 lies at or near the first focus position of the ellipsoidal reflector 5. Thus, light passing through the axial aperture 6a passes through the lens 7. Just as with the device illustrated in FIG. 8, with this lighting device the utilization efficiency of light emitted from the lamp 1 in the forward direction is also improved by arranging a reflective surface in a forward position of the lamp 1.
FIG. 10 illustrates a light source for use with an endoscope as disclosed in Japanese Patent Laid-Open Publication No. 7-175042. Such a light source is composed of a lamp 1, a reflector 8 which creates a nearly collimated luminous flux of the light from the lamp 1, and a collector lens 7 which collects the light from the reflector 8 onto an end surface of a light guide 9. By the arrangement illustrated, light from the lamp 1 can be guided onto the end surface of the light guide 9 so as to be incident within the cone angle of acceptance, as defined by the numerical aperture of the light guide.